Impact arming and tamper switch



July 1, 1969 K. E. POPE 3,453,406

IMPACT ARMING AND TAMPER SWITCH Filed Sept. 8, 1967 Sheet of 2 III 7 3INVENTOR j KENNETH E. POPE ATTORNEYS K. E. POPE July 1, 1969 IMPACTARMING AND TAMPER SWITCH Sheet Filed Sept. 8, 1967 INVENTOR. KENNETH.POPE ATTORNEYS United States Patent 3,453,406 IMPACT ARMING AND TAMPERSWITCH Kenneth E. Pope, Litchfield Park, Ariz., assignor to UMCIndustries, Inc., a corporation of Missouri Filed Sept. 8, 1967, Ser.No. 666,430 Int. Cl. H01h 35/02 U.S. Cl. ZOO-61.45 Claims ABSTRACT OFTHE DISCLOSURE The present invention pertains to impact switches, and,more specifically, to an impact switch responsive to a predeterminedimpact giving rise to a specific fluid pressure to rupture an enclosure.A variety of impact switches have been provided by the prior artutilizing various acceleration responsive elements. A suitableacceleration responsive switch is described in my co-pendingapplication, Ser. No. 648,914, filed June 26, 1967, and assigned to theassignee of the present invention. In that application, the utilizationof the increase in fluid pressure in response to acceleration in anenclosure is described. The present invention utilizes the increasedfluid pressure resulting from an impact to an enclosure containing thefluid to rupture the container. Prior art impact switches do not providemeans for delaying the closure or opening of an electrical circuitimmediately after sensing the impact; the prior art impact responsivedevices immediately result in actuation of the contacts therein inresponse to the detonation of the required acceleration force. Forexample, in such applications as aerially implanted antipersonneldevices, it is necessary to arm tamper and disturb switches after thedevice has struck the ground. However, a delay is necessary after thedevice decelerates upon striking the ground and before arming the tamperand disturb switches to permit vibrations and other disturbances todampen. Prior art impact switches, when placed in such an environmentare incapable of accurately effecting a switch closure after apredetermined time delay following a predetermined impact accelerationforce without substantial sophistication and resulting decreasedreliability.

It is therefore an object of the present invention to provide an impactswitch capable of providing an inherent delay before the actuation ofthe electrical con tacts after the predetermined impact.

It is a further object of the present invention to provide an impactswitch that is relatively insensitive to accelerations and impactsgiving rise thereto less than the predetermined actuation accelerationforce.

It is still another object of the present invention to provide an impactswitch that may be utilized to arm a second switch after a predetermineddelay.

It is still another object of the present invention to provide an armingswitch responsive to a predetermined impact for arming a second switchsensitive to deviation 3,453,406 Patented July 1, 1969 ICC fromhorizontal without regard to the precise attitude of the switches at thetime of arming.

These and other advantages of the present invention will become apparentto those skilled in the art as the description thereof proceeds.

Briefly, in accordance with the embodiment chosen for illustration, avertically aligned cylindrical enclosure containing a fluid such assilicon oil is provided with an electrically conductive float therein. Apair of contacts extend into the enclosure and are positioned such thatthe float can complete an electrical circuit through the contacts. Oneend of the enclosure is rupturable at a predetermined acceleration forcein response to the pressure rise in the fluid caused by the accelerationof the impact. The resulting impact fluid pressure ruptures theenclosure, permitting the fluid to flow into a second enclosurecontaining a floatable platform therein having a tilt-sensitive switchmounted thereon. The resulting interaction of the fluid in the firstenclosure with the ruptured portion of the enclosure permits the closingof an electrical circuit arming the tilt-sensitive switch after apredetermined delay.

The present invention may more readily be described by reference to theaccompanying drawings, in which:

FIGURE 1 is a schematic block diagram of an antipersonnel actuationutilizing the impact switch of the present invention.

FIGURE 2 is a cross-sectional view of an impact arming switchconstructed in accordance with the teachings of the present invention.

FIGURE 3 is a perspective view, partly in section, showing thedeflection means of FIGURE 2.

FIGURE 4 is a perspective view, partly in section, of the floatableplatform of FIGURE 2.

Referring now to FIGURE 1, an anti-personnel device may include thearrangements of elements schematically shown therein.Characteristically, a power source, as a battery 10, provides thenecessary electrical power to explode the device through a bridgewire-type detonator 11. To insure that predetermined conditions existbefore detonation occurs, a variety of control functions are interposedin series with the power source 10 and the detonator 11. A manual armingswitch 12 is usually provided to permit the device to be handled priorto delivery; the arming switch 12 is closed, thus arming the remainingcontrol functions of the device. A diode 14 may be provided to preventreverse current and possible accidental detonation. An impact switch 15is provided and is responsive to a predetermined acceleration forceimparted to the device; for example, the impact switch may be designedto close when a force of 300 gs is exerted thereon, such as by airdelivery, causing the acceleration force to be experienced when thedevice strikes the ground. The impact switch is connected in series witha disturb switch 20 and one or more tamper switches 21. The disturb andtamper switches are connected to the detonator 11 on the side oppositefrom the power supply 10. The impact switch is also connected to a timer23 which may be utilized to close the circuit to the detonator 11through a silicon controlled rectifier 24.

The operation of the application shown in FIGURE 1 may be described asfollows. The device is manually armed by closing the switch 12 prior toair delivery to the target. The device is released from an airplane and,

upon striking the ground, the impact switch is closed. The device isthus armed, and closure of the disturb switch or the tamper switches 21results in detonation. The timer 23 is designed to gate the SCR 24 aftera long delay (e.g., six (6) months). Gating of the SCR 24 also resultsin detonation. The present invention will now be described by referenceto FIGURES 2, 3, and 4; to more readily describe the function of thepresent invention, the terminals A, B, and C have been indicated onFIGURE 1 and in FIGURE 2, thus showing the connection of the presentinvention into the system of FIGURE 1. A first cylindrical enclosure 25contains a fluid 26 such as silicon oil and is provided with anelectrically conductive float 27. When the enclosure 25 is in a normallyupright position as shown in FIGURE 2, the float 27 will remain in thetop thereof. The bottom of the enclosure 25 includes a cap 30 having aconical inner surface 31 terminating in a small opening 32. The cap 30supports electrical contacts 34 and 35 which extend into the enclosure.A frangible or rupturable disc covers the opening 32 in the cap 30 andmaintains the fluid 26 in the enclosure 25. An air bleed passage 41 isprovided in the cap 30 and connects to a capillary tube 42 extendingfrom the cap to the top of the enclosure.

A second cylindrical enclosure is provided and is positioned adjacent tothe rupturable disc 40. The enclosure 50 contains a second fluid whichis most instances will simply be air. An opening 51 is provided in theenclosure 50 and is positioned opposite the opening 32. A fluiddeflecting means 55 is positioned at the top of the enclosure 50 andprovide a conical surface 56 supported by a plurality of legs 57extending from a supporting plate 58 to receive the fluid 26 through anopening 60 and direct the fluid to the inside surface 61 of theenclosure 50. A floatable platform is contained within the enclosure 50and normally rests at the bottom of the enclosure until the fluid 26enters the enclosure 50. The floatable platform is obviously heavierthan the air contained in the enclosure 50, but the toroidal pontoon 72provides buoyancy for the platform when the fluid 26 enters theenclosure 50. A tilt-sensitive switch 75 is mounted on the platform 70and is electrically connected externally to the enclosure 50 throughflexible leads 78 and 79.

In operation, the device of the present invention is oriented so thatthe acceleration forces resulting from impact are substantially in thedirection indicated in FIGURE 2 by the arrow 80. The impact force givesrise to substantial increase in the pressure within the enclosure 25,causing the disc 40 to rupture. The fluid 26 thus flows through therelatively small opening 32, through the openings 51 and 60 onto thesurface 56 of the deflecting means 55. The air within the enclosure 50travels through the passage 41 and capillary tube 42; the capillary tubeas well as the opening 32 is calibrated to permit the fluid 26 to escapefrom the enclosure 25 at a, predetermined rate such that the conductivefloat 27 contacts the electrical contacts 34 and 35 only after apredetermined time delay. Thus, the switch represented by the contacts34 and 35 and the float 27 is not closed until the fluid 26 has escapedthrough the opening 32 down the walls 61 into the enclosure 50. It willbe seen that before the contacts above described are closed, thefloatable platform 70 will he supported by the fluid 26 in the enclosure50.

When the float 27 closes the electrical circuit with the contacts 34 and35, a tilt-responsive switch 75 will become armed. It will be seen thatsince the fluid 26 is now supporting the floatable platform 70 uponwhich the switch 75 is mounted, the platform 70 will assume a horizontalposition without regard to the attitude of the device (within designlimitations which may be, for example, up to 45 from vertical). Thetilt-responsive switch 75 is thus armed and is held in a horizontalposition; any subsequent disturbance of the device giving rise to aslight wave motion or ripple on the surface of the fluid supporting theplatform 70 will cause the tilt switch 75 to close. Tilt-sensitiveswitches may be made responsive to such slight deviations fromhorizontal that merely touching the device of FIGURE 2 will result inswitch closure of the tilt switch 75. It may be seen from FIGURE 1 thata closure of the impact switch and the disturb switch (tilt switch 75)results in detonation. A further inspection of FIGURE 2 reveals that ifthe rest attitude of the device exceeds a predetermined designed maximum(e.g., 45 from vertical), the floatable platform can readily be made tointerfere with the walls of the enclosure 50 such that the tilt switch75 will be closed at the time it is armed by the closure of the contacts34 and 35. The device would therefore be self-destructive in the eventit comes to rest in an unacceptable position.

-It will be obvious to those skilled in the art that the device of thepresent invention may be utilized in a variety of applications otherthan an anti-personnel mine and that applications requiring theactivation of a second switch by a time delay impact switch mayconveniently use the concepts of the present invention. It will also beobvious to those skilled in the art that the present invention wasdescribed in terms of a specific embodiment and that the invention isnot limited by such limiting descriptive terms as cylindrical, normallyopen or normally closed, contacts, and so forth.

I claim:

1. An impact arming switch comprising: a fluid-containing enclosurehaving a rupturable wall; an electrically conductive float positioned ina rest position within said enclosure and having an operative position;a pair of electrical contacts extending into said enclosure andpositioned to be electrically connected by said float when in one ofsaid rest and operative positions and to be electrically disconnectedwhen in the other of said positions; said rupturable wall responsive toa predetermined fluid impact pressure for rupturing and permitting saidfluid to escape from said enclosure; said float responsive to the escapeof fluid from said enclosure for assuming said operative position.

.2. The combination set forth in claim 1 wherein said enclosure is avertically oriented cylinder having a rupturable bottom.

3. The combination set forth in claim 1 wherein said enclosure is avertically oriented cylinder having a rupturable bottom and saidelectrical contacts are positioned in said cylinder adjacent saidrupturable bottom.

4. The combination set forth in claim '1 wherein said electricalcontacts are open when said float is in said rest position and closedwhen said float is in said operative position.

5. The combination set forth in claim 3 wherein said electrical contactsare open when said float is in said rest position and closed when saidfloat is in said operative position.

6. An impact arming switch comprising: a first enclosure containing afirst fluid and having an electrically conductive float therein; asecond enclosure containing a second fluid having a lower density thansaid first fluid and having a floatable platform therein buoyant in saidfirst fluid but not buoyant in said second fluid; a rupturable wallseparating said first and second enclosures responsive to apredetermined fluid impact pressure for rupturing and permitting saidfirst fluid to escape into said second enclosure; a pair of electrical,normally open contacts extending into said first enclosure adjacent saidrupturable wall, said electrical contacts being closed by saidconductive float when said first fluid escapes into said secondenclosure; a tilt switch mounted on said floatable platform responsiveto a predetermined deviation from horizontal, said switch and platformsupported by said first fluid when the latter escapes into said secondenclosure.

7. The combination set forth in claim 6 wherein said pair of electricalcontacts are normally closed and wherein said contacts are opened bysaid conductive float when said first fluid escapes into said secondenclosure.

8. The combination set forth in claim 6 including means connecting saidpair of electrical contacts and said tilt switch in electrical series.

9. The combination set forth in claim 6 wherein said enclosures arevertically oriented cylinders.

10. The combination set forth in claim 6 including fluid deflectingmeans mounted in said second enclosure adja- 10 6 References CitedUNITED STATES PATENTS 3,049,601 8/1962 Hardesty 20061.08 XR 3,086,4684/1963 Mountjoy et a1 102-702 3,167,018 1/1965 Brunner 102-702 ROBERT K.SCHAEFER, Primary Examiner.

M. GINSBURG, Assistant Examiner.

US. Cl. X.R.

